Many types of magnetic data storage media have been developed to store information. They include magnetic hard drives, magnetic diskettes, magnetic tapes, magnetic tape cartridges, hybrid magnetic media such as magnetic-optical disks, and the like. Increasing data storage density is a paramount goal in the development of new or improved types of magnetic data storage media. Cost reduction is another goal.
Magnetic media generally function according to ferromagnetic principles. For example, the surface of a magnetic medium may be coated with one or more magnetic layers, e.g., in the form of a multi-layered magnetic stack or a magnetic alloy. The local magnetization of magnetic domains defined on the magnetic layers can be selectively oriented to encode data. The local magnetizations can then be detected and interpreted in order to read the recorded data. A hysteresis curve typically defines how the magnetic domains can be oriented or reoriented in response to application and removal of magnetic fields.
A number of techniques have been developed to increase storage densities and improve quality and reliability of magnetic media. For example, new and improved coatings have been developed over the years in an effort to improve quality and performance of magnetic media. Also, seed layers have been developed to enhance the quality and performance of the subsequently deposited magnetic layers. A seed layer refers to a layer of a magnetic medium that can control or define the crystal texture of subsequently deposited layers. For example, a seed layer may help define the crystal phase, and the crystalline orientations of subsequently deposited layers, and may improve the magnetic properties of subsequently deposited layers.
Magnetic media can be categorized as longitudinal or perpendicular. Most conventional magnetic media are longitudinal. In longitudinal media, magnetic anisotropy lies parallel to the plane of the medium. In other words, in longitudinal media, the magnetic orientation of individual magnetic domains is generally parallel to the surface of the medium.
In perpendicular media, on the other hand, magnetic anisotropy is perpendicular to the plane of the medium. In other words, in perpendicular media, the magnetic orientation of individual magnetic domains is perpendicular to the medium surface. Perpendicular media generally allow for a much higher storage density than can be achieved in longitudinal media. Perpendicular magnetic properties adequate for high density recording are currently achievable with only a limited number of materials.